Carburetor idle fuel control means



April 25, 1961 J. o. sARTO CARBURETOR IDLE FUEL CONTROL MEANS Filed April 7. 1959 EF I i Ill/Ill,

INVENTOR. cS/YR TO JORMA 0 idle fuel flow vacuum line which 2,981,245 'CARBURETOR IDLE FUEL CONTROL MEANS Filed Apr. 7, 1959, Ser. No. 804,831

8 Claims. (Cl. 123-119) This invention relates to carburetors and inparticular to novel means for controlling the idle fuel flow during cold to hot temperature range engine operating conditions.

In carburetors of the typical downdraft type wherein vacuum or pressure conditions existing in the main air intake passage of the carburetor is utilized to draw idle fuel from the fuel bowl and deposit it downstream of the throttle blade through the idle fuel port, the problem exists of over-enriching the fuel mixture during conditions of moderate speed beyond idle speed due to idle fuel flow continuation, and also the problem exists of not providing sufiicient idle enrichment fuel during cold engine operation at fast idle and during tip in or rapid engine acceleration during the cold condition. In these carburetors if the idle fuel flow control is adjusted so as to provide the proper enrichment during relatively high engine speed, the proper idle flow condition is not attained for cold engine operation at idle speeds and vice versa. The pres ent invention provides an idle fuel flow control means which regulates the idle fuel flow to the exact requirements of the engine during all operating conditions whether they be cold, warm, hot, and at any speed within the entire speed range of the engine. This adjustment leads to increased eificiency and performance of the engine.

It is a principal object of this invention to provide an idle fuel flow regulating means which is responsive to the movement of the choke blade to adjust the idle fuel flow.

A specific object of the invention is to provide an adjustable air bleed means for controlling the vacuum in the bleed means is responsive to the position of the choke blade to so regulate the vacuum in the idle fuel line.

Another specific object is to provide a piston controlled A vacuum port for regulating the vacuum in the idle fuel conduit in response to positions of the choke blade and also in response to pressure conditions existing in the main air intake passage of the carburetor.

Further objects and advantages of the present invention will become apparent from the following description and drawings, in which:

Figure 1 represents a cross sectional view of one variation of the idle fuel flow control means;

Figure 2 represents a portion of the device of Figure 1 showing a closed choke position and maximum idle fuel conduit vacuum; and

Figure 3 represents a variation of the device of Figures 1 and 2 utilizing a choke and vacuum operated piston to control the idle fuel conduit vacuum.

In Figure 1 is shown a typical downdraft carburetor having a choke blade 12 and a throttle blade 14 spaced apart and pivotally mounted in a main air intake passage 16. A fuel bowl 18 communicates across main fuel orifice 20 to a main venturi 22 located in passage 16. An idle tube 24 communicates with main jet 20 and with the main air intake passage 16 downstream of the throttle blade 14 by means of an idle fuel port 26 and idle fuel 54 will gradually move to the left flow conduit or vacuum line 28. It is readily seen that as the engine starts and begins to idle with the throttle blade 14 in the closed position as shown in Figure 1, the air pumping propensity of the engine will cause a vacuum to exist in idle fuel conduit 28 to thereby pull fuel from the bowl 18 through main jet 20 and up through the idle fuel tube 24 and hence to the idle fuel port 26, the size of which port is controlled by the adjustable needle 30. A transfer port 32 provides sufiicient fuel flow to theengine through conduit 28 and port 26 to run the engine during the period that sufficient air flow past the main venturi 22 does not exist to pull fuel therethrough in quantities required by the engine.

The idle fuel conduit vacuum control means 34, forming the principal feature of this invention, consists of a vacuum control port 36 communicating with the main air intake passage through bleeds 38. The size of port 36 is controlled by a tapered needle 40 having one shoulder 42 thereon to limit the upward movement of the needle 40 and having another shoulder 44 thereon to abut a spring 46 tending to urge the needle 40 out of the vacuum control port 36. The needle, spring, port, and bleeds are contained in a unitary housing structure 48. As shown in Figure 2 the needle 40 is urged downwardly into the vacuum control port 3*6as the choke blade becomes closed by the action of the thermostatic coil 50. The taper of the needle 40 provides a convenient means to provide progressive adjustment of the air bleed into the idle fuel conduit 28 as the choke blade progresses from an open to a completely closed position represented by Figures 1 and 2. Needle 40 has a maximum diameter less than that of port 36 to allow some air bleed to occur into the idle fuel conduit 28 at closed choke position to provide a means to regulate the maximum idle fuel flow in this conduit. By the use of this vacuum control means 34, the idle fuel flow is readily adjusted to provide the necessary enrichment for cold operating conditions during which the choke blade is urged to the closed position shown in Figure 2 by the cold coil 50. As the choke blade 12 begins to open, the tapered needle 40 is urged upwardly by spring 46 to open the vacuum control port 36 and cause the vacuum in conduit 28 to be reduced to automatically cut back on the idle fuel fiow and prevent overenrichment as the engine and coil 50 become warmed. When the choke is opened to a certain position and idle fuel enrichment is no longer needed, the needle will be completely removed from the vacuum control port 36 and the vacuum in conduit 28 will become diminished to discontinue the idle enrichment fuel. The strength of springs 46 and 50 are chosen to provide the proper operative relationship between the engine temperature and the idle fuel flow necessary for proper combustion.

In the variation of the vacuum control means of Figure 3 the vacuum control port 52 is controlled in size by the piston 54 which is operatively connected by means of link 56 to the choke blade 12. The cylinder 58 is operatively connected to the main air intake passage 16 downstream of the throttle valve 14 through a vacuum line 60.

Piston 54 is thereby made responsive'to the vacuum downstream of the throttle valve to move the piston 54 to the left to urge choke blade 12 to its open position. The thermostatic coil 50, however, opposes this action. As shown in Figure 3, piston 54 will substantially completely close off port 52 when the choke 12. is in its closed position and as the choke is gradually opened the piston under the force of the coil 50 acting in concert with the vacuum condition in line 60 and cylinder 58. To decrease the combined effect of vacuum in cylinder 58 and the unwinding of the bimetallic coil 50, a slot 62 is provided in the wall of cylinder 58 to allow a bleed into cylinder 58 from the intake passage 16 to partially offset the effect of the vacuum in line 60 and to regulate the movement of piston 54 more in accordance with the required bleed of air into the vacuum port 5-2. Also a beveled groove 64 in the cylinder 58 and communicating with control port 52will further regulate the precise amount of air bleed into the vacuum control port as required by engine operating conditions and the position of the choke blade 12. A restriction may be provided in line 69 as desired to further control the vacuum effect on piston 54 and choke 12.

I claim:

1. In a carburetor having a main air intake passage, a thermostatically actuated choke blade pivotally mounted in said passage, a fuel source connected through an idle fuel conduit means to an idle fuel port in said passage,

idle fuel control means operatively connected with said idle fuel conduit means and said choke blade and responsive to movement of said choke blade to regulate the vacuum condition in said idle fuel conduit means.

'2. In a carburetor a main air intake passage, a thermostatically actuated choke blade and a throttle blade spaced apart and pivotally mounted in said passage, a fuel bowl connected through an idle fuel conduit means to an idle fuel port in said passage downstream of said throttle blade,.a vacuum control port in said conduit means, valve means operatively connected to said choke blade and responsive to movement thereof to regulate the pressure in said conduit means, said valve means comprising a needle slidable into and out of said vacuum control port and being resiliently urged therefrom against the force of said thermostatically actuated choke blade.

3. In a carburetor a main air intake passage, a thermostatically actuated choke blade and a throttle blade spaced apart and pivotally mounted in said passage, a fuel bowl connected through an idle fuel conduit means to an idle fuel port in said passage downstream of said throttle blade, a vacuum control port in said conduit means, valve means operatively connected to said choke blade and responsive to movement thereof to regulate the pressure in said conduit means, said valve means comprising a needle slidable into and out of said port and being resiliently urged therefrom by means of a spring against the force of said thermostatically actuated choke blade, said needle being smaller in diameter than said port to allow a controlled bleed into said conduit means at closed choke operating conditions.

4. In a carburetor a main air intake passage, a thermostatically actuated choke blade and a throttle blade spaced apart and pivotally mounted in said passage, a fuel bowl connected through an idle fuel conduit means to an idle fuel port in said passage downstream of said throttle blade, a vacuum control port in said conduit means and communicating with said air intake passage intermediate said choke and throttle blades, valve means operatively connected to said choke blade and responsive to movement thereof to regulate the pressure in said conduit means, said valve means comprising a needle shiftable into and out of said port and being resiliently urged therefrom by means of a spring against the force of said thermostatically actuated choke blade, said needle being tapered and having a smaller maximum diameter than said vacuum control port to allow a controlled air bleed into said conduit means at cold engine operating conditions.

5. In a carburetor a main air intake passage, a thermostatically actuated choke blade and a throttle blade spaced apart and pivotallymounted in said passage, a fuel bowl connected through an idle fuel conduit means to an idle fuel port in said passage, a vacuum control port in said conduit means, valve means operatively connected to said choke blade and responsive to movement thereof to regulate the pressure in said conduit means, said valve means comprising a needle slidable into and out of said port and being resiliently urged therefrom by means of a spring acting against the force of said thermostatically actuated choke blade, said needle being tapered to a smaller diameter than said port to allow a controlled bleed into said conduit means at cold engine operating conditions, said needle being engageable by said choke blade at choke positions in the closed to near closed range.

6. In a carburetor a main air intake passage, a thermostatically actuated choke blade and a throttle blade spaced apart andpivotally mounted'in said passage, 21 fuel bowl connected through an idle fuel conduit means to an idle fuel port in said passage, a vacuum control port in said conduit means, valve means operatively connected to said choke blade and responsive to movement thereof to regulate the pressure in said conduit means, said valve means comprising a vacuum cylinder and a piston slidably mounted therein and operatively connected to said choke blade to slide in said cylinder in response to movement of said choke blade, said vacuum control port communicating with said cylinder and said piston being adapted to vary the area of said port upon movement of said choke blade.

7. In a carburetor a main air intake passage, a thermostatically actuated choke blade and a throttle blade spaced apart and pivotally mounted in said passage, a fuel bowl connected through an idle fuel conduit means to an idle fuel port in said passage, a vacuum control port in said conduit means, valve means operatively connected to said chokeblade and responsive to movement thereof to regulate the pressure in said conduit means, said valve means comprising a vacuum cylinderand a piston slidably mounted therein and operatively connected to said choke blade to slide in said cylinder in response to movement of said choke blade, said vacuum control port communicating with said cylinder and said piston being adapted to vary the area of said port upon movement of said choke blade, and air bleed means in said cylinder in cooperation with said choke blade for varying the choke ,blade opening force of said piston in proportion to engine heat.

8. In a carburetor having a main air intake passage, :1 thermostatically actuated choke blade pivotally mounted in said passage, a fuel source connected through idle fuel conduit means to .idle fuel port means in said passage,

References Cited in the file of this patent UNITED STATES PATENTS Stokes June 11, 1935 Lindsteadt Dec. 16, 1952 

